The present invention relates generally to prosthetic implants and pertains, more specifically, to a modular joint prosthesis, such as a humeral shoulder prosthesis, and a method for implanting such a prosthesis in the natural bone to replace the natural head of a natural joint with a prosthetic implant.
It has been suggested that a humeral prosthesis of a prosthetic shoulder implant can be constructed in a modular fashion in which a prosthetic humeral head is included in a humeral head component selectively coupled, as by an interconnecting taper arrangement, with a humeral stem component. The advantages of such modular construction are described in several prior patents. Among those advantages is the ability to replicate the natural offset between the center of the humerus and the center of the humeral head by providing a connection arrangement for connecting the humeral head component to the humeral stem component with an appropriate offset. A modular construction enables the selection of a humeral head component which provides the desired offset when connected to the humeral stem component of the humeral prosthesis.
The present invention attains the above-outlined advantages of modular construction in a humeral shoulder prosthesis, and includes improvements which enable a surgeon to more readily and better fit the humeral shoulder prosthesis to the needs of a particular implant site so as to more accurately replicate the natural shoulder joint, and to do so interoperatively. In short, the present invention enables a single humeral head component to accommodate a wider range of offset requirements, thereby reducing the number of different humeral head components required to meet the needs of different implant sites. Further, the ability to provide a wider range of offset enables ready selection of a humeral head component for use in connection with implant sites which have experienced shoulder fractures and where it is desired to gain back arm length lost as a result of a foreshortened humerus ordinarily associated with a shoulder fracture.
Hence, the present invention attains several objects and advantages, some of which are summarized as follows: Provides a modular prosthesis, such as a modular shoulder prosthesis, and implant method enabling the accommodation of a wider range of offset requirements with a lesser number of sizes of component parts of the prosthesis; enables a more accurate accommodation of a particular offset requirement within the wider range of offset requirements; facilitates the choice and connection of a head component, such as a humeral head component of a shoulder prosthesis, to a stem component, such as a humeral stem component, with an accurate location and desired orientation of the humeral head component on the humeral stem component; allows the use of an appropriate offset provided by a humeral head component selected from a reduced number of sizes of humeral head components to gain back arm length lost as a result of a foreshortened humerus at the site of a shoulder fracture; reduces the requirement for larger inventories of component parts, with concomitant reductions in cost and increases in efficiency, as well as increases in economy of manufacture; provides a simplified construction in a humeral shoulder prosthesis for increased ease and accuracy in use, as well as increased ease of manufacture; provides a wider range of choices to a surgeon in accommodating the various conditions encountered at the implant site in different recipients of a humeral shoulder prosthesis; simplifies the implant procedure while enabling greater accuracy in effecting the implant; exhibits exemplary performance over a relatively long service life.
The above objects and advantages, as well as further objects and advantages, are attained by the present invention which may be described briefly as an improvement in a modular humeral shoulder prosthesis for implant in a natural humerus to replace a humeral head of a natural shoulder joint with a prosthetic implant which is to replicate the natural shoulder joint and in which a humeral head component is coupled with a humeral stem component in a prescribed location and orientation by the interoperative engagement of interlocking tapered connector elements located on the humeral head component and on the humeral stem component, the improvement comprising: a humeral head member including an obverse surface providing a bearing surface following a spherical surface contour having a prescribed radius and a central axis, and a reverse surface extending transverse to the central axis; a humeral stem member including a platform for confronting the reverse surface of the humeral head member, and a stem integral with and depending from the platform; multiple tapered connector elements including at least: a first tapered connector element located on the humeral head member and extending in a first direction spaced transversely from the central axis by a first predetermined offset distance; a second tapered connector element located on the humeral head member and extending in a second direction spaced transversely from the central axis by a second predetermined offset distance, the second predetermined offset distance being different from the first predetermined offset distance; and a third tapered connector element located on the humeral stem member and extending along a connector axis, the third tapered connector element being configured for selective interengagement with either one of the first and second tapered connector elements to secure the humeral head member to the humeral stem member, such that upon engagement of the third tapered connector element with a selected one of the first and second tapered connector elements, and subsequent seating of the humeral head member on the humeral stem member, with the humeral head member placed in a desired orientation about the connector axis and a desired offset location relative to the humeral stem member, the humeral head member is secured to the humeral stem member with the bearing surface placed for optimum replication of the natural shoulder joint.
In addition, the invention pertains to an improvement in a method for implanting a modular humeral shoulder prosthesis in a natural humerus to replace a humeral head of a natural shoulder joint with a prosthetic implant which is to replicate the natural shoulder joint and in which a humeral head component is coupled with a humeral stem component in a prescribed location and orientation by the interoperative engagement of interlocking tapered connector elements located on the humeral head component and on the humeral stem component, the improvement comprising: providing a humeral head member having an obverse surface including a bearing surface following a spherical surface contour having a prescribed radius and a central axis, and a reverse surface extending transverse to the central axis; providing a humeral stem member having a platform for engaging the reverse surface of the humeral head member, and a stem integral with and depending from the platform; providing multiple tapered connector elements including at least a first tapered connector element located on the humeral head member and extending in a first direction spaced transversely from the central axis by a first predetermined offset distance, a second tapered connector element located on the humeral head member and extending in a second direction spaced transversely from the central axis by a second predetermined offset distance, the second predetermined offset distance being different from the first predetermined offset distance, and a third tapered connector element located on the humeral stem member and extending along a connector axis, the third tapered connector element being configured for selective interengagement with either one of the first and second tapered connector elements to secure the humeral head member to the humeral stem member; engaging the third tapered connector element with a selected one of the first and second tapered connector elements, with the humeral head member placed in a desired orientation about the connector axis at a desired offset location relative to the humeral stem member; and subsequently seating the humeral head member on the humeral stem member, with the humeral head member placed in the desired orientation about the connector axis and at the desired offset location relative to the humeral stem member, to secure the humeral head member to the humeral stem member with the bearing surface placed for optimum replication of the natural shoulder joint.
In addition, the invention includes an improvement in a modular prosthesis for implant in a natural bone to replace a head of a natural joint with a prosthetic implant which is to replicate the natural joint and in which a head component is coupled with a stem component in a prescribed location and orientation by the interoperative engagement of interlocking tapered connector elements located on the head component and on the stem component, the improvement comprising: a head member including an obverse surface providing a bearing surface following a spherical surface contour having a prescribed radius and a central axis, and a reverse surface extending transverse to the central axis; a stem member including a platform for confronting the reverse surface of the head member, and a stem integral with and depending from the platform; and multiple tapered connector elements including at least: a first tapered connector element located on the head member and extending in a first direction spaced transversely from the central axis by a first predetermined offset distance; a second tapered connector element located on the head member and extending in a second direction spaced transversely from the central axis by a second predetermined offset distance, the second predetermined offset distance being different from the first predetermined offset distance; and a third tapered connector element located on the stem member and extending along a connector axis, the third tapered connector element being configured for selective interengagement with either one of the first and second tapered connector elements to secure the head member to the stem member, such that upon engagement of the third tapered connector element with a selected one of the first and second tapered connector elements, and subsequent seating of the head member on the stem member, with the head member placed in a desired orientation about the connector axis and a desired offset location relative to the stem member, the head member will be secured to the stem member with the bearing surface placed for optimum replication of the natural joint.
Further, the invention includes an improvement in a method for implanting a modular prosthesis in a natural bone to replace a head of a natural joint with a prosthetic implant which is to replicate the natural joint and in which a head component is coupled with a stem component in a prescribed location and orientation by the interoperative engagement of interlocking tapered connector elements located on the head component and on the stem component, the improvement comprising: providing a head member having an obverse surface including a bearing surface following a spherical surface contour having a prescribed radius and a central axis, and a reverse surface extending transverse to the central axis; providing a stem member having a platform for confronting the reverse surface of the head member, and a stem integral with and depending from the platform; providing multiple tapered connector elements including at least a first tapered connector element located on the head member and extending in a first direction spaced transversely from the central axis by a first predetermined offset distance, a second tapered connector element located on the head member and extending in a second direction spaced transversely from the central axis by a second predetermined offset distance, the second predetermined offset distance being different from the first predetermined offset distance, and a third tapered connector element located on the stem member and extending along a connector axis, the third tapered connector element being configured for selective interengagement with either one of the first and second tapered connector elements to secure the head member to the stem member; engaging the third tapered connector element with a selected one of the first and second tapered connector elements, with the head member placed in a desired orientation about the connector axis at a desired offset location relative to the stem member; and subsequently seating the head member on the stem member, with the head member placed in the desired orientation about the connector axis and at the desired offset location relative to the stem member, to secure the head member to the stem member with the bearing surface placed for optimum replication of the natural joint.